Protective masks have long been used to protect the wearer in hazardous environments from inhaling contaminants and potentially harmful materials. They provide a protective, breathable environment to the wearer in contaminated and environmentally threatening conditions, such as fires, chemical spills, radiological events, etc. that might be faced by firefighters, first responders, etc. Protective masks are typically configured with a facemask and valved assemblies for controlling the flow of air to and from the interior of the mask.
The entrance of air into the mask interior may be (by way of non-limiting example) through one or more filters, from self-contained breathing apparatus (SCBA), or through powered air purifying respirators (PAPR), or other air supply mechanisms as may be known to those having ordinary skill in the art.
More particularly, in one mask configuration, air is drawn into the mask interior through the wearer's inhalation, creating a negative pressure environment inside the mask (with respect to ambient air pressure), with the air typically being drawn into the mask through one or more air purifying filter canisters. As the user exhales, a positive pressure is created in the interior of the mask, and a check valve typically opens to allow the exhaled air to exit the mask through an outlet. In this configuration, a simplistic negative pressure valve is typically used to prevent contaminated air from entering through the outlet during the wearer's inhalation.
Likewise, in another mask configuration, air is supplied to the mask in a SCBA system from an air supply, such as an air tank, which provides a positive pressure environment inside of the mask. As the wearer inhales, a supply valve opens to allow air into the mask from the tank. As the user exhales, the supply valve closes and the check valve opens to release the exhaled air out from the mask.
Still further, in yet another mask configuration, air is supplied to the mask in a PAPR system from a motorized blower that delivers filtered air to the mask, again creating a positive pressure environment insider of the mask. The pressure supplied by the blower is typically lower than pressure supplied through a SCBA system, and is thus sent from the blower (at times through a supply valve), through a hose and into the interior of the mask. Once again, as the wearer exhales, the supply valve closes and the check valve opens to release the exhaled air from the mask.
A challenge exists, however, in that the above-described varying mask configurations, each of which is particularly desirable for a particular set of threat conditions, require variously configured exhalation valves. Specifically, the pressure that the exhalation valve must maintain in order to not inadvertently open and allow contaminated air into the mask will vary with the pressure created inside of the mask environment, which in turn will vary with the protective equipment configuration being used (i.e., whether such configuration includes filter canisters mounted to a mask, a PAPR system, a SCBA system, or other systems). Moreover, the pressure that the user must overcome by the check valve to allow their exhaled air to exit must likewise be balanced so as to not excessively stress the wearer. Thus, in the event that a wearer must change their protective equipment due to a changing threat environment, they typically will not only need to change the protective equipment itself, but likewise will need to change the exhalation valve configuration in order to provide an exhalation assembly that is properly fitted to the selected protective equipment.
Even further, given the harsh operating conditions in which such protective mask assemblies are used, the exhalation assemblies are quite prone to damage due to prolonged exposure to the threatening environment. Unfortunately, however, in typical exhalation units used with such protective masks, the exhalation valve assemblies are complex and enclosed, requiring that the entire unit be replaced in the event that individual components of the exhalation valve assembly require service or replacement.
It would therefore be advantageous to provide an exhalation valve assembly for use with protective masks that is easily adaptable to use with varied personal protective equipment configurations without changing out the exhalation valve structure, that is less complex than previously known exhalation valve assemblies, and that allows easy breakdown so that the wearer may easily service the components of the exhalation valve unit.